Studies are conducted in glass branching tubes having branch-to-trunk area ratio of .4-1.4 and an angle of branching of 70 degrees. When the flow in the branches was equal, flow separation did not occur either during steady or pulsatile flow. During unevenly distributed flow, separation occurred in the partially occluded branch. Spiraling of flow seems to be related to the absence of flow separation. Spiraling was found to depend upon the branch-to-trunk area ratio and the configuration of the flow pulse.